Syncing send/receive when piping

README.md

@@ -33,7 +33,26 @@ Usage of ./wsd:
   -url string
       WebSocket server address to connect to (default "ws://localhost:1337/ws")
   -version
-      Display version number```
+      Display version number
+```
+
+### Piping
+
+One can piping multiples messages by breaking them with new lines  
+E.g.
+```
+echo 'a
+b' \
+| wsd -url="wss://echo.websocket.org"
+```
+results
+```
+> a
+< a
+> b
+< b
+```
+
 
 ## Why?
 

main.go

@@ -9,6 +9,8 @@ import (
 	"os"
 	"sync"
 
+	"strings"
+
 	"github.com/fatih/color"
 	"golang.org/x/net/websocket"
 )
@@ -23,12 +25,14 @@ var (
 	displayHelp        bool
 	displayVersion     bool
 	insecureSkipVerify bool
+	isPipe             bool
 	red                = color.New(color.FgRed).SprintFunc()
 	magenta            = color.New(color.FgMagenta).SprintFunc()
 	green              = color.New(color.FgGreen).SprintFunc()
 	yellow             = color.New(color.FgYellow).SprintFunc()
 	cyan               = color.New(color.FgCyan).SprintFunc()
 	wg                 sync.WaitGroup
+	wgReceive          sync.WaitGroup
 )
 
 func init() {
@@ -65,13 +69,15 @@ func printErrors(errors <-chan error) {
 			os.Exit(0)
 		} else {
 			fmt.Printf("\rerr %v\n> ", red(err))
+			doneReceive()
 		}
 	}
 }
 
 func printReceivedMessages(in <-chan []byte) {
 	for msg := range in {
 		fmt.Printf("\r< %s\n> ", cyan(string(msg)))
+		doneReceive()
 	}
 }
 
@@ -84,6 +90,12 @@ func outLoop(ws *websocket.Conn, out <-chan []byte, errors chan<- error) {
 	}
 }
 
+func doneReceive() {
+	if isPipe {
+		wgReceive.Done()
+	}
+}
+
 func dial(url, protocol, origin string) (ws *websocket.Conn, err error) {
 	config, err := websocket.NewConfig(url, origin)
 	if err != nil {
@@ -143,13 +155,34 @@ func main() {
 	go printErrors(errors)
 	go outLoop(ws, out, errors)
 
+	fi, err := os.Stdin.Stat()
+	if err != nil {
+		panic(err)
+	}
+	isPipe = fi.Mode()&os.ModeNamedPipe != 0
+
 	scanner := bufio.NewScanner(os.Stdin)
 
 	fmt.Print("> ")
 	for scanner.Scan() {
-		out <- []byte(scanner.Text())
+		text := scanner.Text()
+		if isPipe {
+			// Ignoring empty lines
+			if len(strings.Trim(text, "")) == 0 {
+				continue
+			}
+			fmt.Println(green(text))
+			wgReceive.Add(1)
+		}
+		out <- []byte(text)
+		if isPipe {
+			wgReceive.Wait()
+			continue
+		}
 		fmt.Print("> ")
 	}
 
-	wg.Wait()
+	if !isPipe {
+		wg.Wait()
+	}
 }